I’ll cry if I want to—measuring glucose levels in your tears

If you look closely, you’ll see a tiny sensor beneath the eye. Inside there are nano-size biosensors which can detect your glucose levels in your tears (or sweat, if prefer). For a diabetic, checking glucose levels has to be done daily by pricking the skin to draw blood.

With this nano-sized biosensor, diabetes patients can measure their glucose levels with the fluid from the tears of their eyes. (copyright Fraunhofer IMS)

Sept. 4, 2012 news item on Nanowerk provides more details,

Pricking a finger everyday is just part of everyday life for many diabetes patients. A non-invasive measurement approach could release them from the constant pain of pin pricks. The linchpin is a biosensor engineered by Fraunhofer researchers: A tiny chip combines measurement and digital analysis – and can be radioed to a mobile device.

The Sept. 3, 2012 news release from Fraunhofer, an application-oriented research organization, provides more detail about the technology and its advantages,

The principle of measurement involves an electrochemical reaction that is activated with the aid of an enzyme. Glucose oxidase converts glucose into hydrogen peroxide (H2O2) and other chemicals whose concentration can be measured with a potentiostat. This measurement is used for calculating the glucose level. The special feature of this biosensor: the chip, measuring just 0.5 x 2.0 millimeters, can fit more than just the nanopotentiostat itself. Indeed, Fraunhofer researchers have attached the entire diagnostic system to it. “It even has an integrated analog digital converter that converts the electrochemical signals into digital data,” explains Tom Zimmermann, business unit manager at IMS. The biosensor transmits the data via a wireless interface, for example to a mobile receiver. Thus, the patient can keep a steady eye on his or her glucose level. “In the past, you used to need a circuit board the size of a half-sheet of paper,” says Zimmermann. “And you also had to have a driver. But even these things are no longer necessary with our new sensor.”

The minimal size is not the only thing that provides a substantial advantage over previous biosensors of this type. In addition, the sensor consumes substantially less power. Earlier systems required about 500 microamperes at five volts; now, it is less than 100 microamperes. That increases the durability of the system – allowing the patient to wear the sensor for weeks, or even months. The use of a passive system makes this durability possible. The sensor is able to send and receive data packages, but it can also be supplied with power through radio frequency.

The glucose sensor was engineered by the researchers at Noviosens, a Dutch medical technology firm. Since it can be manufactured so cost-effectively, it is best suited for mass production.

This looks pretty exciting. Of course, I’d still like to see find out the level of accuracy for this new way to measure glucose as compared to the current technique (no mention of clinical trials). Also, how do you affix the sensor to your skin? Is there a glue? Can you accidentally wash, wipe,  or knock your sensor off? Or, is it difficult to remove? For people who do choose to wear it beneath an eye, how does makeup affect the sensor?

Assuming that the accuracy is the same or better and that any pitfalls due to wearing a sensor have been addressed, I imagine the next hurdle will be scaling up production.

As for the ‘I’ll cry if I want to’ part of the headline for this piece, I have shamelessly borrowed [corrected 2:27 pm PDT, Sept. 5, 2012] from Lesley Gore’s 1963 hit, ‘I’s my party and I’ll cry if want to’. I’ve never loved the lyrics (for the most part) but the chorus has a haunting quality (as far as I’m concerned). Here is Lesley Gore,

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